Exfoliated Graphite Nanosheets Coating on Nano-grained SnO2/Li4Ti5O12 as a High-Performance Anode Material for Lithium-Ion Batteries.

The SnO2/Li4Ti5O12/C compound was gained via hydrothermal, sintering, and ball milling methods. Nano-grained SnO2/Li4Ti5O12 are homogeneously wrapped in a sheet-like graphite. Li4Ti5O12 possesses cyclic stability and superior rate capacity. Meanwhile, the SnO2/Li4Ti5O12 hybrid can supply abundant active sites for absorption of Li+, mitigate chemical stress in cycling, and prevent the ultrathin graphite nanosheets from stacking. Besides, the sheet-like graphite could reduce volume variation in cycling and reduce transmission distance for the electron or Li+. Therefore, an outstanding electrochemical property of the SnO2/Li4Ti5O12/C composite can be obtained.

Mo-Doped SnO2 Nanoparticles Embedded in Ultrathin Graphite Nanosheets as a High-Reversible-Capacity, Superior-Rate, and Long-Cycle-Life Anode Material for Lithium-Ion Batteries.

A new ternary Mo-SnO2-graphite composite has been constructed via hydrothermal and ball milling. The Mo/SnO2 hybrids were homogeneously dispersed in graphite nanosheets. In the Mo-SnO2-graphite, Mo can inhibit the Sn nanoparticle aggregation, enhance the reversible conversion reaction in lithiation, and improve the electrochemical performance. Consequently, the Mo-SnO2-graphite composite contributes a high capacity of 1317.4 mAh g-1 at 0.2 A g-1 after 200 cycles, remarkable rate property of 514.0 mAh g-1 at 5 A g-1, and long-term cyclic stabilization of 759.0 mAh g-1 after 950 cycles at 1.0 A g-1. With outstanding electrochemical performance and facial synthesis, the ternary Mo-SnO2-graphite is a hopeful anode material for lithium-ion batteries (LIBs).

Carbon Quantum Dots-Derived Carbon Nanosphere Coating on Ti3C2 MXene as a Superior Anode for High-Performance Potassium-Ion Batteries.

Potassium-ion batteries (PIBs) are receiving increasing attention at present because of their cheap and lithium-like charge/discharge processes. Nevertheless, the large potassium-ion radius leads to poor potassium intercalation/depotassium kinetics and unstable structure, hindering their development. Here, we synthesized a novel carbon quantum dot-derived carbon nanosphere-encapsulated Ti3C2 MXene (CNS@Ti3C2) composite by polymer pyrolysis, while carbon nanospheres were derived from carbon quantum dots. The composites can suppress the layer stacking of Ti3C2 and prevent oxidation, thereby stabilizing the layered structure of Ti3C2 MXene and improving the cycle life. Besides, carbon nanospheres can increase the specific surface area and active sites, and then more potassium ions can enter the electrode material and boost the reversible capacity. Further, carbon nanospheres are embedded between the Ti3C2 layers, which can increase the interlayer spacing, and the potassium ions are more easily inserted and extracted, thereby improving the potassium storage power and rate performance. The CNS@Ti3C2 composite possesses an excellent synergy, resulting in a high reversible capacity of 229 mAh g-1 at 100 mA g-1 after 200 repeated cycles and a long cycle life of 205 mAh g-1 at 500 mA g-1 after 1000 repeated cycles with high coulombic efficiency (above 99%). This work offers a novel strategy to utilize carbon with MXene in energy storage.